Use nested allocation candidates

Placement added support for allocation candidates query against nested resource provider trees in microversion 1.29. Nova's scheduler report client needs to start using the new microversion to enable adding support for vGPUs, bandwidth and cyborg devices reported as nested RPs under the compute node RP.

Approved for Stein as a specless blueprint. This is adding the nova client-side implementation/support for nested resource providers which are modeled in the Placement service. There is no spec since there are no anticipated API changes to Placement at this point. -- mriedem 20180920